An integrated storage system capable of coping with a plurality of types of protocols such as FCP (Fibre Channel Protocol for SCSI), iSCSI (internet SCSI), CIFS (Common Internet File System), and NFS (Network File System) is gathering attention. Such an integrated storage system is called a unified storage and have advantages such as space saving, a low cost, and improved workability (PTL 1). FCP and iSCSI are protocols for accessing a storage apparatus in units of blocks (hereinafter this access will be referred to as a “block access” hereinafter). CIFS and NFS are protocols for accessing a storage apparatus in units of files (hereinafter this access will be referred to as a “file access”). PTL 1 discloses a computer provided with a host OS including a block processing unit that reads and writes data in units of blocks, a virtual OS including a file server that transmits and receives data in units of files, and an inter-OS communication path through which the host OS and the virtual OS perform communication.